It has long been known to apply plastic or other heat shrinkable labels to bottles and other containers by wrapping a length of heat shrinkable label material around a container to form a sleeve around said container and then heating the sleeve to cause it to shrink into interfacial engagement with the sidewall of the container. In forming the sleeve it is important to have a good seal at the seam. This is accomplished by overlapping the edges and sealing the inside surface of a short portion adjacent one edge to the outside surface of a short portion adjacent the other edge either by solvent, adhesive or heating sealing. See for example U.S. Pat. No. 5,415,721 the disclosure of which is incorporated herein by reference.
According to one widely used process, a length of label material is wrapped around a mandrel and sealed. The sealed sleeve is then placed over the container from the top or bottom. The container and label are then exposed to heat causing the sleeve of the label material to shrink to the contour of the container. Since a separate mandrel was used to form the sleeve, the sleeve could be placed on fairly complex shaped containers and then shrunk.
Under another prior art process, a length of label stock is wrapped around the container, an adhesive is used to seal the leading and trailing edges of the label together and the combination is then heated to shrink the sleeve to the container forming the label. Although, this system provides a low cost method of applying a shrinkable label to the container, it is limited to containers having substantially cylindrical shapes. Thus, in this case the label stock was wrapped around the container and sealed using the container as a wrap mandrel in contrast to the previously described process in which the sleeve was formed by wrapping a length of label stock around a mandrel.
In the first described process a large, very expensive machine was needed to perform the required tasks. On one series of such machines, hot sealing bars were used to seal the leading and trailing edges to form the seam of the sleeves on the mandrel. In a modification of the mandrel process, hot air was directed to the desired sealing area. In both these cases (hot bar, hot air) the complexity of the sealing system not only required expensive mechanical systems, the change over from one container size or design to another required extended periods of time for the mechanical changes of the expensive tooling. It also required an extended period of time to bring the machine up to speed and proper temperature for heat sealing resulting in a great amount of expensive scrap being generated. Companies using the sleeve on mandrel approach usually had very long runs of the same container. As a result, the start up time, tooling cost and scrap rates were not major issues.
The present invention provides method and apparatus capable of labeling complex container shapes as can be done with the mandrel sleeve process while reducing the cost, complexity of equipment, and start-up time needed with such mandrel/sleeve process. The invention also provides reduced tooling costs, machine start-up times and reduced scrap generation.
The system of the present invention includes a stand alone mechanism for effecting sealing of a short length (¼″ to ⅜″) of label stock adjacent the trailing edge to a short length of label stock adjacent the leading edge to form a cylindrical sleeve which may be placed over a container and heat shrunk thereon to form the label. The stand alone mechanism is driven (either mechanically or electrically) to be synchronized with the mandrel turret and provides for introducing a heated surface, a flow of hot air, a solvent material or an adhesive to the sealing position between the overlap of the leading edge and trailing edge length of the label material as it completes being wrapped around the mandrel.
Under one embodiment, a nozzle rotates on one rotatable turret at a speed which matches the speed of a mandrel with a wrapped label rotating on a mandrel turret and, through a cam action, provides a dwell of the “nose” of the nozzle in the sealing area to provide means for sealing the trailing edge portion to the leading edge portion and then, through the cam action retracts from the seal area. In operation, the nozzle matches the speed of the label overlap, dwells, relative to the turret, for a portion of the turret rotation while supplying the heating or other adhesion means into a gap which is momentarily present between the trailing end portion and the leading end portion, and then retracts. The mechanism rotates a number of sealing devices in time with the various mandrels on the turret on which the mandrels are carried.
Since the nozzles are carried on a rotatable turret which is separate from the mandrel turret wrapping device, it has a significantly smaller mass than prior art mandrel-type machines. It can be brought up to operating temperature and speed quickly thereby reducing the start up times of the overall process.